When comparing Mozilla Thunderbird vs Unibox, the Slant community recommends Mozilla Thunderbird for most people. In the question“What are the best e-mail clients for macOS?” Mozilla Thunderbird is ranked 4th while Unibox is ranked 13th.
Ranked in these QuestionsQuestion Ranking
Pro Free (as in freedom and beer)
Pro Lightning Calendar and Address Book integration
Pro Good filtering system
Mozilla Thunderbird offers a flexible filtering system with the ability to set flags and read/unread, as well as sort/assign to new mail directories. There are also numerous plugins available to assist in the filtering.
Pro Consistent and involving a moderate learning curve
The app design of Mozilla Thunderbird has not changed significantly since its beginning, making its learning curve almost non-existent.
Pro Available on Linux, OS X and Windows
Pro Large assortment of plugins available
Mozilla Thunderbird offers a huge amount of extensions to expand the usability and options of the client.
Pro Very reliable
Version after version, Mozilla Thunderbird works as expected.
Pro Tabs for navigation
Pro Send large files easy
Install pCloud plugin for Thunderbird and your files (upto 20 GB free storage included) will be received as download links
Pro Simple, clean interface
Unibox's interface is very clean and easy to understand. It has a classic two-pane interface with all users that have sent emails on the left side and any email currently being read on the right.
Every UI element is only visible when needed. For example, every time you hover on a discussion the trash can, which is otherwise invisible appears.
Pro All emails are sorted by contact
Pro Makes it easy to keep track of different discussions
Unibox groups different emails by user instead of subject. This makes it easy to keep track of messages sent to a particular person and to keep track of different discussions.
Con Development slowed to only focus on stability and security
Mozilla Thunderbird has slowed down its development of features to only focus resources on security and stability.
Con Subject lines can (temporarily) disappear from the list
This is sporadic behavior.
Con Serious bugs
Clicking on a subject line can bring up the wrong email.
Con Outdated interface
Thunderbird's interface is very outdated and unpleasant. It feels more like a Windows XP application than like a modern MacOS one.
Con Terrible integration with macOS
Simple things - drag/dropping pictures doesn't work, for instance.
Con Sends empty emails
Other than syncing issues and displaying wrong badge numbers, Unibox sometimes sends empty emails to people in the user's contact list, which is quite annoying.
Con A number of recurring issues
There are some recurring issues with Unibox: these include the sync dropping and e-mails not reaching their destination.